1. Field of the Invention
The present invention relates to a dampening arrangement in an offset press, and particularly to a dampening water spraying device provided in such an arrangement and including a removable nozzle.
2. Description of the Prior Art
Generally, offset presses are provided with dampening arrangement for supplying dampening water prepared with various additives onto printing plate surfaces or onto peripheral surfaces of rollers leading to the printing plates, and particularly, printing machines in off-set newspaper presses (hereinafter simply called “newspaper presses”) are often provided with dampening arrangement. Dampening water spraying devices (hereinafter simply called “spraying devices”) to be used in the dampening arrangement mainly include those of a so-called single fluid type wherein pressurized dampening water is pushed out and sprayed. In such a spraying device, pressurized dampening water is supplied into the spraying device, and the water is alternately stopped and flowed by an operation of an electromagnetic opening/closing valve such that the dampening water is intermittently sprayed from a nozzle attached to a tip end side of the electromagnetic opening/closing valve.
The prior art concerning a nozzle for spraying dampening water to be utilized in the aforementioned spraying device includes that disclosed in Japanese Patent No. 3035371. As shown in FIG. 1 and FIG. 2, the spraying device described in the Japanese Patent No. 3035371 includes: a nozzle 20f having an orifice 23f; a nozzle holder 30f for supporting the nozzle; a nozzle fixing member 40f in a nut shape for fixing the nozzle to the nozzle holder; and an electromagnetic opening/closing valve 13f for alternately stopping and flowing dampening water; such that the dampening water is appropriately sprayed by the operation of the electromagnetic opening/closing valve 13f. The nozzle 20f is to be fixed to the nozzle holder 30f by the nozzle fixing member 40f, and the attachment and detachment of the nozzle 20f to and from the nozzle holder 30f is to be conducted by a tool. Upon attachment of the nozzle 20f, the nozzle 20f is inserted into the nozzle fixing member 40f, and the nozzle fixing member 40f is threaded by a tool onto a male screw 52f provided at the tip end portion of the nozzle holder 30f, while the nozzle fixing member 40f is also loosened by the tool such as when the spray of the dampening water becomes defective.
The spraying device of the prior art disclosed in the Japanese Patent No. 3035371 has such a problem to be solved. Namely, the spraying device of the prior art is intended to spray the dampening water atomized to have a uniform particle diameter from the orifice of the nozzle, by adjusting a supplying pressure of the dampening water so as to improve the printing quality. However, it is extremely difficult to spray the dampening water of a uniform particle diameter from the orifice of the nozzle over a long time, and the orifice is narrowed as the same is used overtime, because the additives contained in the dampening water are deposited and accumulated to a portion around the orifice. It is also inevitable that the orifice is suddenly clogged with foreign matters during long-term usage, thereby changing a spraying state. If this changed state is left alone, the dampening water is not properly sprayed, thereby causing such a serious defect including not only a deteriorated printing quality but also a contaminatedly printed paper face due to lack of the dampening water. As such, it is necessary for a responsible person to replace the nozzle before such a situation, but the working efficiency upon nozzle replacement has been extremely low because attachment and detachment of the nozzle is to be conducted by the tool.
It is also typical in newspaper presses to provide eight pieces of nozzles per one printing cylinder capable of printing a sheet of paper having a 4-page width. However, recent newspapers have been remarkably developed into an increased number of pages and into colorization, and one example of printing by a set of newspaper presses includes a situation for printing a newspaper having 48 pages inclusive of 24 pages to be printed in 4 colors, thereby requiring 48 pieces of nozzles for monochrome printing of 24 pages and requiring 192 pieces of nozzles for color printing of 24 pages, thereby resulting in 240 pieces of nozzles to be used. Usually, newspaper publishers often possess a plurality of sets of newspaper presses, and such an increased number of nozzles far exceeding the aforementioned 240 pieces are to be subjected to maintenance, such that the nozzle maintenance becomes an extremely heavy burden to a responsible person in a position for managing the printing quality.